Protective overcoating



May 15, 1934.,

FiledMay 29, 1930 2 Sheets-Sheet l Density.

500 wavelengtfi Way 1 n m. ammo; EarleEiRichardaon & Cyril J82? y 1934E. E. RICHARDSON El AL 1,958,714

PROTECTIVE OVERCOATING Filed May 29, 1950 2 Sheets-Sheet 2 Bensiiy.

7. celluloseAJceiaie 2% Orfiho Diphergl Benzene fi-CelluloseAcefaieconiaininy Z Meta, Di henyZ/Benzene. QCelluloseAnehlte containing 2%parupzwhenyl Benzene and 10% Trlgphenyl Phosphate.

1Q "celluloseAcefide cbniuinhgg 1% Amfizz'acene.

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Patented 15, 1934 PROTECTIVE OVERCOATIN G Earle E. Richardson and CyrilJ. Staud, Rochester, N. Y., assignors to Eastman Kodak Company,Rochester, N. Y., a corporation of New York Application May 29, 1930,Serial No. 457,508

12 Elaims.

This invention relates to new types of protective coatings andparticularly to cellulose acetate overcoatings which are applied overlacquer or other surfaces whereby the latter are protected from theshort rays of light.

The cellulose nitrate lacquer industry has increased greatly in the pastfew years due, inpart at least, 'to the ease with which this lacquer maybe coated upon metallic and other surfaces, and

to the rapidity with which these lacquer coatings dry. In the automotiveindustry particularly its use has released considerable of the materialswhich formerly were held in process and has, therefore, decreasedmarkedly the expense incidental to the coating and finishing of theautomobile. From the consu'mers standpoint, however, cellulose nitratelacquers have not appreciably increased the period of time during whichhis automobile or other lacquer finished go product is kept fromcorrosion or in which it retains its initial glossy and freshappearance,- it being a well known fact that cellulose nitrate loses itsgloss with relatively great rapidity when exposed to the elements. Thede-lustering and decomposition of cellulose nitrate surfaces, while tosome extent due to inclement weather conditions, is primarily due to theultra-violet rays from the sun which penetrates and decomposes thesurface layer.

While the addition of pigments, gums, and plasticizers to the cellulosenitrate compositions aids to a slight extent in rendering the cellulosenitrate layer less affected by the ultra-violet light, the protectionthey afford is not by any means complete. With even a considerableamount of these constituents in the lacquer there is, nevertheless, uponthe surface a good proportion of the cellulose nitrate directly exposedto the solar radiation. Moreover it has been found that the exposedcellulose nitrate under such conditions will be decomposed by theultraviolet light incident to its surface. Furthermore, decomposition ofthe exposed cellulose nitratc will auto-catalyze the underlyingcellulose nitrate particles which are in intimate contact with them.This auto-catalysis of the cellulose nitrate creeps through the wholesurface with ever increasing velocity, with resultant decompositionwhich destroys much of the former lustre of the surface. To obviatethese difiiculties it has been suggested that a high gloss varnish orother transparent material be overcoated on the cellulose nitrate orother coating to inhibit its breakdown. While it has been previouslysuggested in the application of Paul C. Seel, Serial No. 425,353, toovercoat nitrate lacquers with a clear lacquer containing celluloseacetate, we find that the protective efiect of such acetate lacquercoatings may be materially improved, particularly from the standpoint oflight protection, so by preparing it in accordance with our invention.

An object of the present invention is to provide a filter for theabsorption of the short light rays. Another object is to provide acellulose actate surface or overcoating which absorbs subes stantiallyall the ultra-violet light which has a deleterious eilect upon theunder-coating. Another cbject is to provide a cellulose acetate, lacquerwhich having been applied in the usual manner absorbs many of thedecomposing light so rays. Other objects will hereinafter appear.

In our former U. S. application Serial Number 410,708, filed November30, 1929, we have disclosed that cellulose acetate compositions whichcontain small percentages of napthalene as or chlorinated naphthalenesuch as alpha or beta chloronaphthalene have that property of inhibitingthe passage of ultra-violet light. We have now found that the polycyclichydrocarbons generally and their derivatives all have this unexso pectedproperty of inhibiting the passage of ultra-violet light. Under thisgeneral class of chemical compounds, naphthalene, chloronaphthalene,anthracene, phenanthrene, and ortho.

meta and para-diphenylbenzene when present in ca cellulose acetatecompositions all act as filters to prevent the passage of ultra-violetlight.

In our research on these compounds we have found that in spite of thefact that triphenyl phosphate has the same number of phenyl groups so ashas phenanthrene or the diphenyl benzenes, nevertheless, triphenylphosphate will not act as a suitable filter for the ultra-violet.Benzene alone also does not act as such a filter. We con-- cluded,therefore, that the benzene rings should 95 be fused as they are inphenanthrene or joined directly together as in the diphenyl benzenes ifthe compound is to act as an ultra-violet filter of sufficient opacityto protect such coatings and such proved to be the case, as allpolycyclic hydro carbons which we have been able to obtain and test haveproven to be suitable ultra-violet filters. Also the followingnitrogen-containing organic compounds have been found to have thisquality of absorbing ultra-violet light to a greater or lesser degree,namely, diphenylguanidine, paminobenzoic acid, phthalimide,nitroanisole, nitrobenzol, quinaldine, benzyl benzoate, glycerol butylphthalate, and B methoxyethyl phthalate no as set forth in separateapplications of Staud,

Richardson, Murray and Kocher, respectively.

Fig. 1 shows the absorption of light rays, unplasticized cellulosenitrate and acetate, and plasticized cellulose acetate.

Fig. 2 shows the effect on absorption by additions of phenanthrene andnaphthalene.

combination of a spectroscope and photometer into a single instrumentwhich enables not only the wave length at which absorption takes placeto be measured, but also the intensity of such absorption. In theaccompanying drawings the abscissa: represent wave lengths in terms ofmillimicrons (1 millimicron equals 10 Angstrom units). On the ordinatesare plotted the optical densities, the optical density being thelogarithm of the reciprocal of the transmission. Expressedmathemetically, it In represents the incident light and I1 the emergentlight, then it follows that the transmission is a fraction of the totalincident light represented as I1/Io some having been absorbed by thematerial. The converse of the transmission would, of course, be opacityand be expressed by l/T with T as the transmission. This, expressed interms of the original symbols would be In I1 and the optical density isequal to the logarithm to the base ten of the opacity.

The accompanying table may be of assistance in reading the technicalspectrophotometric terms and the attached drawings:

Transmission Opacity Density 'that the use of cellulose acetate alone inthe overcoating for cellulose nitrate lacquers would be entirelyinefiective in afiording protection from ultra-violet light since theentire absorption curve of cellulose acetate lies in a shorter wavelength than those of cellulose nitrate shown by curve 1, Figure l, themain portion of the curve lying between 230 and25'0 millimicrons. Inthis instance, of course, the cellulose acetate had no light filterpresent therein.

Cellulose acetate as an overcoating for cellulose nitrate, however, maybe used as a vehicle for other materials, since in theterrestrial-atmosphere no ultra-violet light of wave lengths 230 to 250millimicrons occur. This is due to the presence of a sharp absorptionband produced by what is thought to be due to ozone or other lightfiltering material in the earth's upper atmosphere which absorbspractically all the radiation between 220 and 288.5 millimicrons,

tered out.

It is thus evident that the cellulose acetate itself will not decomposeas rapidly as cellulose nitrate when subjected to the suns rays, as therays which decompose it do not reach the surface of the earth.

From a consideration of the above discussion, it will be realized thatalthough cellulose acetate of itself does not decompose appreciablyunder the effect of ultra-violet light, it will not protect an underlayer of cellulose nitrate over which it may be coated for the reasonthat it does not absorb those light rays which decompose the nitrate. Bya review of the accompanying curves it will be seen that theultra-violet absorption power of the cellulose acetate can be moved tothe right of the cellulose nitrate curve, by the addition of the properlight filters thereto, thereby protecting the cellulose nitrate whensuch a cellulose acetate composition is overcoated thereon. In Figure 1,curve 3, is shown the effect of adding an ordinary plasticizer such as10% triphenylphosphate to a cellulose acetate composition. While theoriginal cellulose acetate curve has been shifted somewhat to the rightby adding triphenylphosphate nevertheless it has not been shiftedsufficiently to give to the acetate composition sufiicient filteringquality to protect the cellulose nitrate. This phenyl containingcompound, therefore, while it contains three phenyl groups does not havethe required filtering qualities for removing the deleteriousultra-violet rays, as has been fully discussed hereinabove. The additionof 5% chloronaphthalene to the cellulose acetate film shown in Figure 2,curve 5, however, carries the acetate curve well to the right of thecellulose nitrate curve, thereby showing that such an overcoating ofcellulose acetate will prevent all wave lengths of light less than 320millimicrons from affecting any subcoatings upon which the celluloseacetate coating may be placed. In Figure 2, curve 4, is shown the efiectof the addition of 5% naphthalene to cellulose acetate, here too it willbe noted that the curve is sufficiently well to the right of thecellulose nitrate curve to afiord good protection. The excellentabsorption qualities of a cellulose acetate containing phenanthrene iswell shown in Figure 2, curve 6. It will be noted here that a film ofthis nature containing even as low as 2% phenanthrene will absorb allthe light rays shorter than 380 millimicrons. Figure 3 shows the effectof the ortho, meta and para-diphenyl benzenes when added in amounts ofapproximately 2% to the cellulose acetate. Curve 7 in this figureillustrates the filtering qualities of ortho-diphenyl benzene whichabsorbs approximately all the light shorter than 300 millimicrons, curve8, which is the result of a test on cellulose acetate containing 2% ofmeta-diphenyl benzene shows a total absorption of approximately alllight shorter than 300 millimicrons, while curve 9 for para-diphenylbenzene shows a somewhat better absorption of all light shorter than 320millimicrons. Curve 10 for anthracenc carries the absorption stillfurther to the right substantially all short waves under 390millimicrons being fil- As has been stated heretofore, while theaddition of a larger quantity of these filter compounds to celluloseacetate will afiord a somewhat greater absorption of the ultra-violet,this increase is generally not in proportion to the additional compoundused. For example, in the case of chloronaphthalene, 1% will cut out allthe short waves. of approximately 310 millimicrons while 5% ofchlorinated naphthalene only increases this absorption to waves ofapproximately 320 protection to under coatings from ultra-violetmillimicrons. The addition of large quantities,

therefore, of the filtering ingredient is not generally required oradvantageous. It may also be stated that the meta and ortho diphenylbenzenes are readily soluble, at least up to 10%, in the usual solventsfor cellulose acetate butthat the para diphenyl benzene is not soreadily soluble from .2 to .5 of one per cent being the usual amountwhich can be dissolved up in the usual solvents. However as will be seenfrom the above, the addition of certain plasticizers such astriphenylphosphate assists in retaining the para diphenyl benzene insolution in amounts up to 2% or even more.

The amount of these filters required to afiord radiations are of suchsmall magnitude that no appreciable plasticizing eflect would beobserved. When present in the cellulose acetate layer in such amounts,therefore, they in no appreciable way afiect the plasticity or the otherphysical qualities of the overcoating, but merely act as filters,preventing the passage therethru of the ultra-violetlight. A largeramount of these substances in the cellulose acetate coating does not inany way lower the filtering efiect but has a tendency to slightlyincrease the opacity of the film to the ultra-violet. In some instancesthe presence of 20, 30 to 50 per cent of the-light filter, which is alsosuitable as a plasticizer, will eliminate the necessity of adding aseparate plasticizer to the film. Whether or not the filter ingredientsshould be added in sufficient amounts to act also as plasticizers willin each case be determined by the type of filter used. Some of thefilters are not particularly useful for thisdual purpose because whenthey are present in a cellulose acetate film in amounts over and abovethatrequired to make the film opaque to the ultra-violet, theingredients themselves objectionably tint or color the film. In anyevent the applications of Kosher, Serial Nos. 457,505 and 457,506 ofeven date cover thisfeature. If the filter then is to be employed inamounts only s'ufiicient to give the desired filtering eifect tothefilm, generally this requires from approximately -5%, and a secondplasticizer such as triphenyl phosphate, alpha chloronaphthalene or thelike many of which are well known in this art may be added in sufiicientamounts to give the desired degree of plasticity;

We have found that it is not material what type of vehicle holds thefilter as suitable varnishes, gums. shellacs, etc. for some purposes areequally as usefulas incorporating the filter in a cellulose derivative.Nor should we be understood to restrict ourselves tocellulose acetateparticularly as an overcoating cellulose derivative vehicle. There arenumerous other such esters of cellulose, the mixed organicesterscellulose aceto-propionate, cellulose aceto benzoate, etc., themixed inorganic organic esters-cellulose nitro acetate, cellulosephospho acetate etc., or for that matter the other aliphatic organicesters of cellulose such as cellulose propibnate, cellulose butyratesetc., many of which are useful in which to incorporate the filter foruse as an overcoating. In selecting the vehicle it must, of course, beborne in mind that only those which are themselves not as rapidlydecomposed, as the subcoating which they are used to protect, are bestsuited.

Our novel filters may be prepared in the fol-' lowing manner altho anymethod of incorporating them in the particular vehicle which uniformlydisperses the light filter thruout the vehicle may generally be used.For example the cellulose acetate may be mixed with 3 to 10% of thelight filter with or without the addition of say 50% of a plasticizer.This mixture may then be dissolved in a suitable solvent or solvent mix:ture such as one made up of 15% ethyl acetate, 50% acetone, 20% ethyllactate and 15% denatured alcohol,approximately one gallon of thissolvent being required for 20 ounces of cellulose acetate. For theincorporation of some of the light filters other solvents or solventmixtures may be more suitable, the above example being given merely toacquaint those skilled in the art with one manner of incorporating thefilter. We

are, therefore, not to be limited by the details or proportions of thisexample except as may be indicated by the app-ended claims.

It is evident from a study of the above disclosure that our inventioncovers the use of any type of filtering medium in a cellulose acetateovercoating which acts therein to render the same opaque to the passageof ultra-violet light, thereby protecting the sub-coating fromdeterioration due to this light. Cellulose acetate overcoatingscontaining sufficient amounts of the hereinabove indicated filters, orany suitable vehicle containing these filters will come within the scopeof this invention, without sacrificing any of the advantages resultingtherefrom. Also the term overcoating and the description of theseovercoatings in connection with lacquers is to be understood broadlyrather than specifically as it will be apparent that the value of ourinvention lies in the fact that by interposing between the cellulosenitrate layer and the source of the ultra-violet rays, a vehiclecontaining the ultraviolet light filter the nitrate underlayer will beprotected from decomposition and deterioration. Thus, the celluloseacetate overcoating may consist of an already formed sheet containingthe filter, which sheet is interposed between the cellulose nitratesheet to be protected and the source of the ultra-violet light.Furthermore in the case of laminated glass, for instance, the cellulosederivative reinforcement interposed between the glass laminations mayconsist of a cellulose nitrate interlayer on either side of which iscoated or otherwise imposed a layer or coating of a vehicle such ascellulose acetate with which has been incorporated an ultra-violet lightfilter. Thus, even tho the'cellulose nitrate interlayer be covered onboth sides with glass it is first covered with a vehicle containing anultra-violet light filter so that the cellulose nitrate is protectedfrom decomposition by the ultra-violet light which would otherwisepenetrate the cellulose nitrate and decompose it. Thus, the termovercoating used in this specification and the appended claims is not tobe confined to a mere lacquer top coat but is to be construed broadly asany shielding layer containing an ultra-violet ter for preventingdecomposition of cellulose nitrate by ultra-violet light.

What we claim as our invention and desire to be secured by LettersPatent of the United States is:

1. An article of manufacture which has a closely adhering lacquercoating decomposable by sunlight, and a light-filtering overcoatingcomprising a cellulose organic derivative and a light-filteringsubstance, the overcoating being substantially transparent to visiblelight and having the characteristic, due to its content of thelight-filtering substance, that it is absorbent of substantially all therays of light shorter than 320 closely adhering lacquer coatingdecomposable to substantially completely prevent decomp0sition of thelacquer coating.

2. An article of manufacture which has a by sunlight, and alight-filtering overcoating comprising a cellulose mixed organicderivative and a light-filtering substance, the overcoating beingsubstantially transparent to visible light and having thecharacteristic, due to its content of the light-filtering substance,that it is absorbent of substantially all the rays of light shorter than320 millimicrons, the light-filtering substance being present in theovercoating in an amount suflicient to substantially completely preventdecomposition of the lacquer coating.

3. An article of manufacture. which has a closely adhering lacquercoating decomposable ,by sunlight, and an overcoating which comprises anorganic derivative of cellulose and a polycyclic hydrocarbon, theovercoating being substantially transparent to visible light and havingthe characteristic, due to its content of the polycyclic hydrocarbon,that it is absorbent of substantially all the rays of light shorter than320 millimicrons, the light-filtering substance being present in theovercoating in an amount sufficien-t to substantially completely preventdecomposition of the lacquer coating.

4. An article of manufacture which has a closely adhering lacquercoating decomposable by sunlight, and an overcoating which com= prisescellulose acetate and. a polycyclic hydrocarbon, the overcoating beingsubstantially transparent to visible light and having thecharacteristic, due to its content of the polycyclic hydrocarbon, thatit is absorbent of substantially all the rays of light shorter than 320millicrons, the light-filtering substance being present in theovercoating in an amount sufiicient to substantially completely preventdecomposition of the lacquer coating.

5. An article of manufacture which has a closely adhering lacquercoating decomposable by sunlight, overcoated with a cellulose acetatecomposition containing a light-filtering substance, the overcoatingbeing substantially transparent to visible light and having thecharacter- 1 istic, due to its content of the light-filtering substance,that it is absorbent of substantially all the rays of light shorter than320 millimicrons,

' the light-filtering substance being present in the the overcoatingbeing substantially transparent to visible light and having thecharacteristic, due

to its content of the light-filtering substance, that it isabsorbent-*of substantially all the rays of light shorter than 320millimicrons, the light- 1 tering substance being present in theovercoating'in an amount suiiicient to substantially completely preventdecomposition of the lacquer coating.

'7. An article of manufacture having a closely adhering cellulosenitrate lacquer coating with an overcoating of cellulose acetatecontaining a polycyclic hydrocarbon, the overcoating being substantiallytransparent to visible light and having the characteristic, due to itscontent of the polycyclic hydrocarbon, that it is absorbent ofsubstantially all the rays of light shorter than 320 millimicrons, thelight-filtering substance being present in the overcoating in an amountsufl'icient to substantially completely prevent decomposition of thelacquer coating.

8. An article of manufacture having a closely adhering cellulose nitratelacquer coating with an overcoating of cellulose acetate containing fromapproximately 4% to 5% of a polycyclic hydrocarbon, the overcoatingbeing substantially transparent to visible light and having the char-.acteristic, due to its content of the polycyclic hydrocarbon, that it isabsorbent of substantially all the rays of light shorter than 320millimicrons.

9. An article of manufacture having a closely adheringcoatingdecomposable by sunlight, and an overcoating comprising a celluloseorganic derivative containing phenanthrene, the overcoating beingsubstantially transparent to visible light and having thecharacteristic, due to its phenanthrene content, that it is absorbent ofsubstantially allthe rays of light shorter than 320 millimicrons.

10. An article of manufacture having a closely adhering coatingdecomposable by sunlight, and an overcoating comprising celluloseacetate containing phenanthrene, the overcoating being substantiallytransparent to visible light and having the characteristic, due to itsphenanthrene content, that it is absorbent of substantially all the raysof light shorter than 320 millimicrons.

11. An article of manufacture having a closely adheringcoatingdecomposable by sunlight, and a light-filtering overcoatingcomprising a cellulose organic derivative containing anthracene, theovercoating being substantially transparent to visible light and havingthe characteristic, due to its anthracene content, that it is absorbentof substantially all the rays of light shorter tha 320 millimicrons.

, 12. An article of manufacture having aclosely adhering coatingdecomposable by sunlight, and

a light-filtering overcoating comprising cellulose acetate containinganthracene, the overcoating being substantially transparent to visiblelight and having the characteristic, due to its anthracene content, thatit is absorbent of substantially all. the rays of light shorter than 320millimicrons.

' EARLE E. RICHARDSON.

CYRIL J. STAUD.

